Partially overlapping hologram motion picture record

ABSTRACT

In a motion picture record in which successive frames of a motion picture are manifested by a series of successive holograms, such as phase holograms, greater redundancy and a saving in record material are achieved by having each one of the holograms partially overlap both the hologram which immediately precedes and the hologram which immediately succeeds that hologram in the series. The problem of unwanted spatial beat frequencies, which results from such overlap and is dependent on the amount of such overlap, can be eliminated by restricting the amount of overlap to a value such that the minimum spatial beat frequency is less than the ultimate resolution of the playback system (e.g. closed circuit television) employed in reconstructing the motion picture from the motion picture record.

i i t a mmww [111 3,632,869 v- [72] Inventors Robert Alfred BartoliniOTHER REFERENCES P u Reid, High-Speed Photography- Proc of the 8thInternag g y Lune: East Brunswick both of tional Congress Stockholm,June 1968, pp. 3 l4- 3 l 6 [21] AWL 376,660 Primary Examiner-DavidSchonberg [22] Filed Nov. 25, 1969 Assistant Examiner-Ronald J. Stern[45] Patented Jan. 4, 1972 Attorney-Edward J. Norton [731 Assignee RCACorporation ABSTRACT: In a motion picture record in which successive[54] PARTIALLY OVERLAPPING HOLOGRAM frames of a motion picture aremanifested by a series of suc- MOTION PICTURE RECORD cessive holograms,such as phase holograms, greater 5 Claims, 5 Drawing Figs Wm redundancyand a saving in record material are achieved by g having each one of thehologl 'amgp agrally overlap both the [52] US. Cl 178/63, hologram whichjggmediately precedes and "the hologram 350/ wmhimm'gfdiately succeedsthat hologram in the series. The lnt. f of unwanted patia] beatfrequencies results 3/00 from such overlap and is dependent on theamount of such [50] Field of Search 350/35; 5

overlap, can be eliminated by restricting the amount of over- 178/65, Elap to a value such that the minimum spatial beat frequency is less thanthe ultimate resolution of the playback system (e.g.

[56] References cued t closed circuit television) employed inreconstructing the mo- FOREIGN PATENTS tion picture from the motionpicture record. 1,139,955 1/1969 Great Britain 350/35 502\ pommuousMOTION PICTURE g k 506 PHASE HOLOGRAM E PRESSING PHOTOSENSITIVE SURFACE5|2 TELEVISION CAMERA r MEANS M l T.V. SIGNAL TRANSLATING MEANSTELEVISION VIEWING MEANS PATENTEDJAN m A I 3.632.869

SHEET 1 or 2 A h El/K *NON-OVERLAPPING PHASE HOLOGRAM OVERLAPPING PHASEHOLOGRAM- MOTION PICTURE TAPE MOTION PICTURE TAPE (PRIOR ART) Fig 2.

Flgo 1.

DRIVE /3OO n -r I NON-DIFFUS|NG 302 PLURAL BEAM l REDUNDANCY MEANS l4LA\SER Q'Q 13-22-9253 A A AA MOTION PICTURE TRANSPARENCIES SHUTTER y-RECORDING SYSTEM 342 Fig. 3.

I VEVTORS Robert 11. Ba rtolini and Michael J Lurie. BY fea /0?.

ATTORNEY PATENTEDJM 4m: 3.532.869

SHEET 2 0F 2 Fig. 4.

502\ commuous MOTION PICTURE DRWING 506 PHASE HOLOGRAM MEANS PRESSINGLASER PHOTOSENSITIVE SURFACE 5|2 5|0 504 TELEVISION i L 9 /T h CAMERA aMEANS P I 7 W 2 500 514 T.V. 5 SIGNAL 518 TRANSLATING -PLAYBACK SYSTEM-MEANS TELEVISION VIEWING ig. 5. v MEANS INVENIORS Robert A. Bartolim'and Michael J. Lurie BY pe 'gJ f/ d ATTORNEY PARTIALLY OVERLAPPINGHOLOGRAM MOTION PICTURE RECORD This invention relates to holography and,more particularly, to motion picture records in which the frames of amotion picture are manifested by a series of successive holograms.

A technique has been developed for mass producing record pressings inwhich a record pressing, such as a vinyl disk or tape, has a series ofphase holograms impressed therein which manifest the pictorialinformation in successive frames of a motion picture.

Briefly, in accordance with this technique, each of the successiveframes of a motion picture are respectively recorded, in turn, inholographic form as separate ones of a series of phase hologramsarranged in a predetermined format on an optical-recording medium, suchas a photoresist for instance. This provides a master recording fromwhich a metallic mold of the series of phase holograms may be built upby a process which may include the steps of electroless plating orvacuum deposition of a thin metallic layer which faithfully copies thephase hologram master recording, followed by an electroplated metallicbacking for this layer. This metallic mold may be employed in massproducing, by pressing, replications of the master recording on aplastic medium such as vinyl.

Playback means, including a readout beam source, such as a laser, meansfor moving the pressed record with respect to the readout beam and aclosed circuit television system responsive to the reconstructed phaseholograms of the series, may be employed to view the motion picturerecorded in holographic form on the pressed record.

In the past, it has been the practice to record successive ones of thephase holograms in the series in juxtaposed, nonoverlapping,substantially contiguous relationship with respect to each other.

It has now been found that certain advantages result if the lap betweenadjacent holograms. One consequence of this is that in the case where aseries of phase holograms is oriented along the length of a tape, sothat the metallic mold and the pressed record are also in the form of atape, a greater number of holograms may be impressed in a given time atany given speed (inches per second) of the tape movement. This increasesthe output of the impressing machinery. Another consequence is the factthat the tape may be moved at a slower speed during playback, so that ittakes a smaller length of tape to provide a given program time. A secondadvantage of partially overlapping phase holograms is the fact that anyflicker effect which may be present in playing back the prior art seriesof nonoverlapping phase holograms, due to possible spacing, which mayexist between the end of a preceding hologram and the beginning of thenext succeeding hologram, is eliminated. However, the most importantadvantage to be gained by partially overlapping successive ones of theseries of phase holograms is the increased signal-to-noise ratioachieved by the greater redundancy which results therefrom.

Although partially overlapping successive phase holograms in the seriesof phase holograms provides all of the above=set forth advantages, italso may produce an undesired result. In particular, partiallyoverlapping successive phase holograms cause the playback reconstructedimage of any of these holograms to contain unwanted spatial beatfrequencies having a minimum value which depends upon the amount ofoverlap between adjacent phase holograms in the series. However, thisproblem may be obviated by limiting the amount of overlap betweensuccessive phase holograms to a value which makes the resulting minimumspatial beat frequency no less than the ultimate resolution of theplayback system.

It is therefore an object of the present invention to provide animproved motion picture record system in which successive frames of amotion picture are manifested by a series of successive phase hologramson a record and in which each one of the phase holograms partiallyoverlaps both the phase hologram which immediately precedes and thephase hologram which immediately succeeds that one of the phaseholograms in the series.

This and other objects, features and advantages of the present inventionwill become more apparent in the following detailed description takentogether with the accompanying drawing, in which:

FIG. 1 is a schematic showing of a strip of tape on which prior artnonoverlapping phase hologram motion pictures have been recorded;

FIG. 2 is a schematic showing of a section of tape on which overlappingphase hologram motion pictures have been recorded in accordance with atechnique of the present invention;

FIG. 3 is a diagram of a recording system for recording a series ofphase holograms manifesting the frames of a motion picture;

FIG. 4 is a graph showing the effects of the nondiffusing plural beamredundancy means of FIG. 3, and

FIG. 5 is a diagram of a playback system for playing back a motionpicture record on which successive frames of the motion picture aremanifested by a series of phase holograms.

Referring now to FIGS. 1 and 2, FIG. 1 shows five successive holograms,I'l -H of a series of such holograms oriented along the length of tapesection 10, while FIG. 2 shows the same five holograms Il -H orientedalong the length of tape 20. In FIG. 1, the five holograms are arranged,as in the prior art, in nonoverlapping relationship, while in FIG. 2 thefive holograms are arranged in accordance with the present invention inpartially overlapping relationship. As shown, in both FIGS. 1 and 2, therespective holograms of the series are substantially the same size aseach other.

Although in practice the shape of each individual hologram is normallyrectangular, it has been shown as circular in both FIGS. 1 and 2. Thereason for doing this is that partially overlapping circles may be shownwith much greater clarity than partially overlapping rectangles. SinceFIGS. 1 and 2 are schematic showings, and the particular shape of eachof the series of phase holograms does not form part of the presentinvention, it is to be understood that the shape of each of holograms HH in:both FIGS. 1 and 2 may be rectangles of the same size as eachother, rather than circles as shown schematically in FIGS. 1 and 2.

A comparison of FIG. 2 with FIG. 1 shows that the five partiallyoverlapping holograms l-h-l-l, occupy a smaller distance along thelength of tape section 20 of FIG. 2 than that occupied by the series ofsimilar nonoverlapping holograms H ,-H along the length of tape section10 of FIG. 1.

Referring to FIG. 3, there is shown a preferred embodiment of a systemfor recording holograms in the format shown in either FIG. I or in theformat of FIG. 2. In FIG. 3, drive shutter motor 300, as indicated bydashed lines, mechanically controls the operation of shutter 302 and themovement of motion picture transparencies 304, as well as the motion ofrecording medium 306, which is shown as a length of tape covered with alayer of photoresist, by advancing means 308 coupled to medium 306.

Laser 310 operates at a wavelength M. In response to a momentary openingof shutter 302, laser 310 applies a beam of wave energy 312 to beamsplitting partially reflecting mirror 314. The first component of waveenergy 316 is transmitted through beam splitter 314, then is enlarged bya beam enlarger including lenses 318 and 320 to form a relatively widecollimated beam of wave energy 322. Nondiffusing plural beam redundancymeans 324, which may be composed of a two dimensional phase gratinghaving a certain line spacing or, alternatively, a beam-splitting mirrorsystem or an optical tunnel, transforms collimated beam 322 into adiscrete number of partially overlapping beams of wave energy 326 whichare slightly angularly displaced from each other. The position of motionpicture transparencies is such that a single frame of the motion pictureis simultaneously illuminated by'all of the discrete number of beams326. This frame is oriented in the focal plane of convex lens 328.Therefore, the plurality of redundant information beams 330 emergingfrom the motion picture transparency frame then being illuminated by theplural beams 326 is transformed into parallel information beams 332 bylens 328. Aperture plate 334, having an aperture of a certain area forpassing a portion of information beams 332 located directly in front ofa first given area of recording medium 306, which is then in cooperativerelationship therewith. The aperture in aperture plate 334 has adimension of length h in a direction parallel to the direction of motionof recording medium 306. Therefore, only a first given area of recordingmedium 306 having this length dimension h is exposed by the wave energyfrom information beams 332 impinging thereon.

A second component of wave energy 336 is reflected by beam splittingmirror 314, and is then further reflected by mirror 338 and enlarged bya beam enlarger including lenses 340 and 342 to fonn collimatedreference beam 344. The direction of reference beam 344 is such as toalso expose the first area of recording medium 306 which is incooperative relationship with the aperture of aperture plate 334. Thisexposure of the first area of recording medium 306 takes placesimultaneously with the exposure thereof by information beams 332 whenshutter 302 is momentarily opened by drive shutter motor 300. Thisresults in a holographic interference pattern being recorded on thisfirst given area of recording medium 306.

After a hologram interference pattern is recorded on a first given areaof recording medium 306, advancing; means 308 may be operated by driveshutter motor 300 to move recording medium 306, which is in the form ofa tape, a given distance in a direction oriented along the length of thetape. This causes a second given area of recording medium 306 to bebrought into cooperative relationship with the aperture in apertureplate 334. Shutter 302 may then be operated momentarily again to recordthe next succeeding hologram interference pattern in the series ofholograms to be recorded.

The pictorial information in each successive frame of motion picturetransparency 304 may be manifested by one or more successive hologramsin the recorded series of holograms. For instance, since motion picturesare designed to operate at 24 frames per second while television isdesigned to operate at 60 fields or 30 frames per second, forsynchronization purposes it might be desirable to employ the same givenframe of the motion picture to record each of the first three of a groupof five successive holograms of the series of holograms to be recordedand then employ the next succeeding frame of the motion picture torecord each of the last two of these five successive holograms. In thiscase, the holograms would be played back at a rate of 60 holograms persecond, which is equal to the field rate of a standard televisionsystem. In any case, drive shutter motor 300 is effective in moving eachsuccessive frame of motion picture transparencies 304 into cooperativerelationship with beams 326 at an appropriate time to cause the entireseries of recorded holograms to correspond in informational content withthe motion picture depicted by the successive transparency frames.

In FIG. 3, the purpose of placing lens 328 one focal length in front ofthe frame of motion picture transparency 304 being recorded, so thatthis frame of motion picture transparency 304 lies in the focal plane oflens 328, is to provide an effective object distance for informationbeams 332 which is infinite. This results in each of a series ofrecorded holograms being a so-called Fraunhofi'er hologram. Thedesirability of employing Fraunhoffer holograms will become apparentlater when the playback system of FIG. 5 is discussed in detail below.

The purpose of nondifi'using plural beam redundancy means 324 in FIG. 3is to provide a certain amount of desired redundancy in each recordedhologram interference pattern of the series, without concomitantlyproducing the unwanted speckle noise in the reconstructed image of sucha hologram interference pattern which would result if a diffusingredundancy means were utilized. Such a nondiffusing plural beamredundancy means forms the subject matter of copending US. Pat.application Ser. No. 662,822, filed Aug. 23, I967.

Briefly, as disclosed in this copending patent application, by means ofa phase grating having an appropriate line spacing or, alternatively, bymeans of an appropriate arrangement of a plurality of mirrors, eachhologram may be composed of a discrete number of partially overlappingsubholograms. For instance, in FIG. 4 is h is the length of the apertureof aperture plate 334, parallel information beams 332 may include threesimilar partially overlapping information beams in the vertical plane.Each of these beams has a cross sectional dimension in the verticalplane substantially equal to the length h." The central one of thesebeams is symmetrically disposed with respect to the aperture of apertureplate 334 so that it illuminates substantially the entire area ofrecording medium 306 then in cooperative relationship with the aperture.However, each of the lateral beams in FIG. 4 are so situated that onlyone-half the beam coincides with the aperture in aperture plate 334.Thus, as shown in FIG. 4, the three information beams provide aredundancy of two, with corresponding points on any two of these beamsbeing displaced from each other by a distance s," which is equal toone-half the length h. Each of the three beams gives rise to its ownpartially overlapping subhologram interference pattern during therecording of each respective one of the holograms of the series.

FIG. 4 is confined to only a single dimension, i.e., the verticaldimension. However, if nondifiusing plural redundancy means 324 is a twodimensional phase grating, for instance, partially overlappinginformation beams arranged in a direction into the paper may also beachieved. In this case, nine partially overlapping information beams 332will be obtained to provide an overall redundancy of four.

By resorting to a more complex arrangement of mirrors, the total numberof partial overlapping information beams may be slightly increased withan accompanying slight increase in the amount of redundance achieved.However, any attempt to significantly increase the amount of redundancyby the use of a nondiffusing plural beam redundancy means requires suchcomplex optics that it is not practical at this time. Since thesignal-to-noise ratio obtained is a direct function of the amount of theamount of redundancy which exists in the recorded holograms, it isdesirable to further increase this redundancy without requiring a morecomplex nondiffusing plural beam redundance means. This is achieved bythe present invention.

In the prior art, the distance by which the tape which comprisesrecording medium 306 is advanced by advancing means 308 is madesubstantially equal to or even slightly larger than the length h" of theexposed area of a single recorded hologram. This results in adjacentholograms of the series of recorded holograms being disposed injuxtaposed, nonoverlapping, contiguous relationship with each other, asshown in FIG. 1. In the present invention, the distance by which thetape which comprises recording medium 306 is moved by advancing means308 is made significantly smaller than the length It. This results inadjacent holograms of the series being in partially overlappingrelationship with respect to each other, as shown in FIG. 2. Thiseffectively increases the redundancy and, hence, the signal-to-noiseratio olf'tained without increasing the complexity of nondiffusingplural beam redundancy means 324.

Referring now to FIG. 5, there is shown a preferred embodiment of aplayback system of the present invention.

A transparent plastic tape 500 having a series of partially overlappingphase holograms impressed therein which are oriented along the length ofthe tape, such as shown in FIG. 2, and which were derived from a seriesof phase holograms recorded on a recording medium in the mannerdiscussed above in connection with FIG. 3, is continuously moved byshutterless continuous drive means 502 past readout beam 504 of coherentwave energy from laser 506. Laser 506 operates at a wave length A whichis either the same as or different from the wave length A, employed inrecording the phase holograms. in response thereto, a first orderdiffraction output beam 508 is obtained which contains the motionpicture information recorded in holographic form in the series of phaseholograms. Beam 508 is composed of components corresponding to eachobject point in the motion picture. Each of these components is a planewave formed of parallel rays. In cooperative relationship with beam 508is reconstructing convex lens 5110, having a focal length F which causesa reconstructed image of the phase hologram then being read out to beformed on photosensitive surface 512 of television camera means 514.This is true because photosensitive surface 512 is situated in the focalplane of lens 510. Television camera means 514 scans the reconstructedimage on photosensitive surface 512 to convert it into a video signal,which is then passed through TV signal-translating means 516 totelevision viewing means 518. Elements SM, 516 and 518 constitute closedcircuit television apparatus. Such apparatus may include as part thereofa home television receiver in which the kinescope thereof comprisestelevision-viewing means 513.

The fact that each of the series of phase holograms on transparent tape500 is a Fraunhofier hologram not only causes first order diffractionoutput beam 508 to be formed of plane wave components, but permitstransparent tape 500 to be continuously moved by shutterless means whilebeing continuously illuminated by readout beam 504 without affecting theposition of the reconstructed motion picture image on photosensitivesurface 512. However, reconstructing lens 510 is required in order toreconstruct a motion picture image on surface 512 from the continuouslymoving, partially overlapping series of phase holograms on transparenttape 500.

Due to the fact that adjacent ones of the phase holograms on transparenttape 500 partially overlap each other, the reconstructed image of themotion picture displayed on photosensitive surface 512 will also includeunwanted spatial beat frequencies, the lowest one of which has afrequency given by the following formula:

where s is the distance between corresponding pints of the closestsubholograms which result as a consequence of both of the use ofnondifiusing plural beam redundancy means 324, as discussed above inconnection with FIG. 4, and the partial overlap of successive recordedholograms in the series, as shown in FIG. 2; A is the wavelength ofreadout laser 506; F is the focal length of reconstructing lens 510; andw is the value of the minimum spatial beat frequency appearing in thereconstructed motion picture image formed on photosensitive surface 512.

By way of example, for instance, the minimum spatial beat frequency canbe made equal to about 16 cycles per millimeter by employing a readoutlaser having a wavelength of 633 nanometers with a reconstructing lenshaving a focal length of 50 millimeters, and by providing an amount ofpartial overlap between successive holograms of the series such that theclosest spacing between two adjacent subholograms is about equal to 0.51millimeters.

Spatial beat frequencies, which constitute unwanted noise, cannot beobserved on television viewing means 518 if the ultimate resolutioncapability of the closed circuit television apparatus composed ofphotosensitive surface 512, television .sion apparatus and do notdegrade the camera means 514, TV signal-translating means 516 andtelevision viewing means 518 is made no greater than the minimum spatialbeat frequency of the reconstructed motion picture image formed onphotosensitive surface 5R2. in particular, in the case of the aboveexample, the ultimate resolution capability of the closed circuittelevision apparatus or the motion picture image formed onphotosensitive surface 512 is no greater than 16 cycles per millimeter.Therefore, the unwanted spatial beat frequencies which result frompartial overlapping successive ones of the series of recorded phaseholograms are effectively filtered out by the closed circuittelevimotion picture displayed by television viewing means 518, which iswatched by an observer of the motion picture being played back.

We claim:

ll. In a system for playing back a motion picture record whereinsuccessive frames of a motion picture are manifested by a series ofsuccessive phase holograms each of which has substantially the samegiven size, wherein said system includes said record, means forsequentially illuminating said phase holograms with a readout beam ofwave energy to sequentially obtain reconstructed real images of saidmotion picture frames in a given area of space and image responsivemeans including a wave sensitive surface element coincident with saidgiven area and means coupled to said element for viewing said motionpicture, said image responsive means having a given resolutioncapability; the improvement therewith wherein each one of said phaseholograms partially overlaps by a given amount both the phase hologramwhich immediately precedes and the phase hologram which immediatelysucceeds that one of said phase holograms in said series, whereby saidreconstructed images of said phase holograms includes spatial beatfrequencies having a minimum value which depends on said given amount ofoverlap, said given amount of overlap being of such a value that thevalue of said minimum spatial beat frequency is no less than saidultimate resolution capability of said image responsive means.

2. The system defined in claim 1, wherein said sequential illuminatingmeans includes a laser for providing optical energy at a givenwavelength for producing said readout beam and shutterless means coupledto said record for moving said series of phase holograms in sequence incooperative relationship with said readout beam to continuouslyreconstruct real images of said motion picture frames in said given areaof space and wherein said image responsive means comprises closedcircuit television apparatus including television camera means having aphotosensitive surface element coincident with said given area of spaceand television viewing means for displaying the reconstructed realimages of said motion picture frames picked up by said television camerameans.

3. The system defined in claim 2, wherein each of said phase hologramsis a Fraunhofier hologram, and wherein said sequential illuminatingmeans further includes convex lens means having a given focal length,said lens lying in the path of a first order difiraction beam resultingfrom illumination of said phase holograms by said readout beam with saidphotosensitive surface element lying in the focal plane of said lens.

4. The system defined in claim 5, wherein each of said phase hologramsis composed of redundant displaced overlapping subholograms, wherebysaid minimum beat frequency also depends upon the spacing between saidsubholograms and, hence, the amount of partial overlap betweensuccessive phase holograms of said series to maintain said minimum beatfrequency no less than said ultimate resolution capability of saidplayback system is dependent upon the spacing between saidsubholograrns.

5. The system defined in claim 1, wherein said record is a transparenttape having said phase holograms impressed thereon with said seriesoriented along the length of said tape.

UNITED S'K'AS E ENEIENT @WFHJE Patent No. 363L869 Dated 1/4/72Inventor(S) Robert Alfred Bartolini It is celrtified that error appearsin the above-identified patent and that said Letters Patent are herebycorrected as shown below:

Column 6 line 59, "claim" 5" should read "claim. 3--

Signed am sealed this 19th day of November 197%.

(SEAL) Attest:

McCOY M. GIBSON JR cu MARSHALL DANN Attesting Officer Commissioner ofPatents FORM po'wsc (069) uscoMM-Dc sows-ps9 3530 6'72 u.s. GOVERNMENTPRINTING omcz: I969 osss-a:a

1. In a system for playing back a motion picture record whereinsuccessive frames of a motion picture are manifested by a series ofsuccessive phase holograms each of which has substantially the samegiven size, wherein said system includes said record, means forsequentially illuminating said phase holograms with a readout beam ofwave energy to sequentially obtain reconstructed real images of saidmotion picture frames in a given area of space and image responsivemeans including a wave sensitive surface element coincident with saidgiven area and means coupled to said element for viewing said motionpicture, said image responsive means having a given resolutioncapability; the improvement therewith wherein each one of said phaseholograms partially overlaps by a given amount both the phase hologramwhich immediately precedes and the phase hologram which immediatelysucceeds that one of said phase holograms in said series, whereby saidreconstructed images of said phase holograms includes spatial beatfrequencies having a minimum value which dePends on said given amount ofoverlap, said given amount of overlap being of such a value that thevalue of said minimum spatial beat frequency is no less than saidultimate resolution capability of said image responsive means.
 2. Thesystem defined in claim 1, wherein said sequential illuminating meansincludes a laser for providing optical energy at a given wavelength forproducing said readout beam and shutterless means coupled to said recordfor moving said series of phase holograms in sequence in cooperativerelationship with said readout beam to continuously reconstruct realimages of said motion picture frames in said given area of space, andwherein said image responsive means comprises closed circuit televisionapparatus including television camera means having a photosensitivesurface element coincident with said given area of space and televisionviewing means for displaying the reconstructed real images of saidmotion picture frames picked up by said television camera means.
 3. Thesystem defined in claim 2, wherein each of said phase holograms is aFraunhoffer hologram, and wherein said sequential illuminating meansfurther includes convex lens means having a given focal length, saidlens lying in the path of a first order diffraction beam resulting fromillumination of said phase holograms by said readout beam with saidphotosensitive surface element lying in the focal plane of said lens. 4.The system defined in claim 5, wherein each of said phase holograms iscomposed of redundant displaced overlapping subholograms, whereby saidminimum beat frequency also depends upon the spacing between saidsubholograms and, hence, the amount of partial overlap betweensuccessive phase holograms of said series to maintain said minimum beatfrequency no less than said ultimate resolution capability of saidplayback system is dependent upon the spacing between said subholograms.5. The system defined in claim 1, wherein said record is a transparenttape having said phase holograms impressed thereon with said seriesoriented along the length of said tape.